Static space charge in evaporated ZnS:Mn alternating-current thin-film electroluminescent devices

TitleStatic space charge in evaporated ZnS:Mn alternating-current thin-film electroluminescent devices
Publication TypeJournal Article
Year of Publication1998
AuthorsHitt, J. C., P. D. Keir, J. F. Wager, and S. S. Sun
JournalJournal of Applied Physics
Volume83
Issue2
Pagination1141
Date Published1998
ISSN00218979
Keywordselectroluminescent devices, hole traps, II-VI semiconductors, manganese, phosphors, space charge, thin film devices, zinc compounds
Abstract

The operation of alternating-current thin-film electroluminescent (ACTFEL) devices may be strongly affected by the presence of dynamic or static positive space charge within the phosphor layer during device operation. Dynamic space charge is a positive charge in the phosphor layer which is periodically created and annihilated during each period of the applied voltage waveform. In contrast, static space charge is a positive space charge in the phosphor layer whose charge state does not change appreciably during steady-state operation of the ACTFEL device. The static space charge density of evaporated ZnS:Mn ACTFEL devices is estimated to be ∼ 7×10¹⁶ cm-³ from measured trends in the phosphor clamping field as a function of phosphor thickness. This static space charge density estimate implies a cathode clamping field of ∼ 2.2 MV/cm and a clamping interface trap depth of ∼ 1.5 eV. Furthermore, from transferred charge trends as a function of the phosphor thickness it is concluded that the static space charge in evaporated ZnS:Mn ACTFEL devices arises from metastable hole trapping in the phosphor.

DOI10.1063/1.366806
Short TitleJ. Appl. Phys.